1. Field of the Invention
The present invention relates to a communication relay device relaying communication between an internal network and an external network, and particularly relates to a technique selecting types of external networks to be connected or a communication system.
2. Description of the Related Art
Heretofore, a communication relay device known as a wireless LAN access point is in widespread use as a device enabling a plurality of terminal devices to connect to external networks such as the Internet in residential or corporate settings. The device configures a LAN (Local Area Network) that is an internal network between the device and a terminal device, and is programmed with, for example, a function for routing communication from a communication terminal to an external network, a Dynamic Host Configuration Protocol (DHCP) server function for allocating an Internet Protocol (IP) address for the communication terminal, a Network Address Translation (NAT) function for performing address conversion, a Domain Name System (DNS) server function for converting a domain name and an IP address (DNS forward function), for example.
Such a communication relay device is intended to be installed at a fixed position, and thus, once connected to the external network, it is in principle that a connection destination is not changed. Upon changing it, it is necessary for a user to switch manually from a setting screen, etc., of the communication relay device. In a case of a mobile communication relay device, a communication relay device dedicated to a specific external network does not intend to change the connection destination. When the external network is a wireless LAN, a base station of the connection destination may be changed. This task is often performed manually.
On the other hand, a machine in which a connection destination is automatically changed is known. Wireless LAN access point AT-TQ2403 manufactured by Allied Telesis K.K. of Tokyo, Japan (referenced in Non-Patent Document 1) is provided with a function for automatically setting a channel by sensing surrounding wireless interference. The machine is capable of collectively managing users and collectively setting change by grouping (clustering) a plurality of access points. The device is configured to use an automatic channel management function so as to sense the level of radio wave interference of a nearby existing access point and to automatically change the channel in use of the machine within the cluster so that the interference is decreased.
In this way, a conventional technique includes two methods, i.e., that used when processing for switching base stations is automatically performed by a device, and that used when the same is performed based on a user's own determination. In the former, an algorithm or a parameter is previously determined, and for an opportunity determined thereby, executed switching processing includes scanning for switching base stations or reconstruction of the function. However, it is difficult to change the algorithm or the parameter, and there is a problem in that once the setting is made, it is not possible to flexibly change a connection method. In the latter, when the user is dissatisfied with the communication quality or when the connection is cut, the setting can be arbitrarily made for switching the connections. However, the connection based on the algorithm or the parameter, as described above, cannot be performed.
Japanese Patent Laid-Open No. 2002-141929 discloses a LAN connection device, including a plurality of physical ports, used for automatically performing exclusive connection switching on a connection between networks. This document (Patent Document 1) discloses a configuration in which a packet relay portion relays a packet between channels connected to a plurality of physical ports; a primary system switchable port that shares a channel and is exclusively connected to the shared channel by a switch circuit; a sub-system switchable port; a carrier detection portion that detects a communication carrier from the sub-system switchable port; and a switch control portion that provides control such that the sub-system switchable port is connected to the shared channel when the carrier is detected and the same switches to the primary system switchable port when there is no switch switching demand for a fixed time period from the carrier detection portion.
Japanese Patent Laid-Open No. 2002-141929 also discloses a lock control portion that inhibits switching from the primary system switchable port to the sub-system switchable port. The switch control portion holds a state of the switch circuit during a call with a communication terminal connected to a LAN, and the switch control portion executes a lock demand by the lock control portion when the lock control portion receives communication desiring a lock operation from a communication terminal. With such a configuration, it is configured so that the port is completely automatically switched safely. However, this method does not enable port switching at a user's arbitrary timing.
Another related product is “Wireless Gate Home Antenna for emobile” from TripletGate Inc. of Tokyo, Japan, which is a device that relays a connection to the Internet by High-Speed Download Packet Access (HSDPA) and provides an external connection for a terminal by wireless LAN (referenced in Non-Patent Document 2). This device is capable of Internet connection to a plurality of terminals simply when the device is installed, even in locations where wired networks cannot be utilized.
However, this device can only be connected to a single wireless operator using HSDPA. Therefore, in addition to the inability to be used outside of the HSDPA area, even an area offering a more suitable wireless access system cannot be selected.
Patent Document 1: Japanese Patent Laid-Open No. 2002-141929
Non-Patent Document 1: Internet URL, http://www.allied-telesis.co.jp/info/news/2006/nr061213.html (printed on Feb. 5, 2009);
Non-Patent Document 2: Internet URL, http://www.tripletgate.com/wirelessgate/news/homeantenna.pdf (printed on Feb. 5, 2009)